debug.py

from decorpy import debug

@debug
def factorial(n, acc=1):
    if n < 2:
        return acc
    return factorial(n-1, n*acc)


f5 = factorial(5)

## Output : 
Now calling factorial(5)
Now calling factorial(4, 5)
Now calling factorial(3, 20)
Now calling factorial(2, 60)
Now calling factorial(1, 120)
Call with factorial(1, 120) -> returned 120
Call with factorial(2, 60) -> returned 120
Call with factorial(3, 20) -> returned 120
Call with factorial(4, 5) -> returned 120